1. Technical Field
The present invention relates to a magnetic shield, a program that is used in the selection of the material of the magnetic shield, and a selection method of the material of the magnetic shield.
2. Related Art
In a case when a weak magnetic field is measured as with a magnetoencephalogram or a magneto-cardiograph, it is necessary to isolate only the magnetic field of the measurement target by cancelling, with respect to the measurement target, the far greater magnetic fields, such as geomagnetism, of the external environment. Therefore, in the related art, the environmental magnetic field is cancelled by using a magnetic shield.
As a technology of a magnetic shield that cancels the external environmental magnetic field, a magnetic shield room with a multi-layered structure which is configured so that magnetic permeability becomes gradually lower toward the inner layers using magnetic screening materials with the highest magnetic permeability for the outer layers is described in JP-A-5-327263. Further, a magnetic shield device that combines active and passive magnetic shields is described in JP-A-2008-282983. Further, a magnetic shield device in which a highly conductive material layer on the outside and a magnetic material layer on the inside are formed to be opposed is described in JP-A-2008-288328.